(1) Field of the Invention
This invention is related to vertical shaft impact rock crushers. Rock crusher operators have ordinary skill in this art.
(2) Description of the Related Art
Impact rock crushers have been known for over thirty years. See Miller U.S. Pat. No. 3,174,698 and Bridgewater U.S. Pat. No. 3,174,697. However before this invention the crushers had two major problems. The first was vibration. By adding a large mass of rocks to be crushed the rocks would flow into a impeller rotating at high speed in uneven amounts. With the changing flow of the rocks within the impeller the impeller would almost always be imbalanced and vibrate accordingly.
Another problem was the abrasion. The rocks moved over metal parts within the rotors or impellers and their movement would quickly abrade the parts. Also, larger rocks impacting the impellers required them to be of rather heavy material.
The abrasion problem was at least in part alleviated by forming rock packs or packed material in pockets to provide the surface that the rocks abraded. Such structure is shown for example in the U.S. patents of Bridgewater 3,174,697, Canada 5,145,118, Bartley 4,921,173, Terrenzio 4,513,919, Szalanski 4,560,113 and Watajima 4,844,354. The Sazlanski rock pack of FIG. 5 is of particular interest.
The maintenance costs of a rock crusher is a considerable amount. Before invention, the annual maintenance costs of the rock crusher could be as high as the 21% of the value of the rock crushed.
The percentage of the costs for the maintenance has been calculated of a specific crusher on the basis that spare parts cost $180. per hour of use. The rock crusher crushes about 300 Tons of rocks per hour. The selling price of crushed rock would be about $6. per ton. It is estimated the labor costs for installation of the spare parts would be equal to the cost of the spare parts. In addition, inspection costs of (at $18.00/Hr.) of 0.5 Hr. for every 5 hours of operation is necessary. Therefore the costs of maintenance would be $361.80 per hour. The selling price of the 300 Ton crushed rock per hour would be $1800.00.
It is has been known for over a hundred years that a fluid or fluid-like material could be placed within the rings on spinning structure such as the Withee U.S. Pat. No. 229,787. However, generally these have been used only upon structures which do not have the magnitude of unbalance such as the rotors of rock crushers. For example, Withee was concerned with balancing a millstone which would have basically been symmetrical in any event. He suggested that the fluid-like material could be shot, sand or water.